Chloride ions and the membrane potential of Purkinje fibres

Carmeliet, Edward

doi:10.1113/jphysiol.1961.sp006682

Cited by 216 publications

(104 citation statements)

References 11 publications

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“…As a result, efflux of water from the inside of Purkinje cells may occur and decrease extracellular K+ concentration ([K+]0). It has been shown that both resting potential (Weidmann 1956) and K+ conductance during phase 4 (Carmeliet 1961) In summary, the data from the present experiment suggest that the mechanism for genesis of this VT may not be re-entry but rather enhanced automaticity.…”

Section: Discussionsupporting

confidence: 46%

Observations with endocardial electrography on ventricular tachycardia by intracoronary saline in dogs.

Abe¹

1982

Tohoku J. Exp. Med.

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Selective injection of 1.5 ml of 10% saline into the left circumflex coronary artery (LCX) was carried out during sinus rhythm twice in each of 15 mongrel dogs anesthetized with sodium pentobarbital, and multiple endocardial recordings including His bundle electrogram (HBE) were made. Ventricular tachycardia (VT) was elicited in all of the 15 dogs both in the first and second injections. The cycle length of sinus rhythm before injection was 468+88 msec (mean+s.D.). The coupling interval between the last depolarization of the left ventricle (LV) of sinus origin and the first premature LV depolarization of the VT was 395+57 msec. Coupling interval between the first and the second LV depolarizations was 348+78 msec. Significant difference was noted between any pair of these values (p<0.01). No bundle branch re-entry in the beginning of VT was observed. The site of origin of the VT was referred to the LV in 13 dogs. Rapid pacing during paroxysm of VT applied at the apex of the LV made no marked influence upon VT after pacing. The calcium channel blocker, diltiazem failed to block the production of VT. The mechanism for genesis of this VT may not be re-entry but rather enhanced automaticity independent of the calcium inward current. --ventricular tachycardia; intracoronary injection; endocardial electrography The incidence of VT per se is not quite high, although many methods for experimental production of VT in animal study have been reported (Siebecker et al. 1961;Scherf and Bornemann 1967;Wallace et al. 1967;Bellet 1971;Lown et al. 1977) and ventricular tachyarrhythmias including VT can be induced by these methods. In the previous reports (Abe 1979(Abe , 1980) the author demonstrated with surface electrocardiography (ECG) that VT could be successfully elicited by intracoronary injections of hyperosmotic solutions in canine hearts with 100% incidence. In the present experiments VT produced by intracoronary hyperosmotic saline was studied with endocardial electrography. METHODSFifteen mongrel dogs weighing between 20 and 29 kg (average, 24.6 kg) were anesthetized with intramuscular sodium pentobarbital (35 mg/kg), incubated with a cuffed

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Section: Discussionsupporting

confidence: 46%

Observations with endocardial electrography on ventricular tachycardia by intracoronary saline in dogs.

Abe¹

1982

Tohoku J. Exp. Med.

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“…After a few minutes the membrane potential began to oscillate with a maximum amplitude of 30 mV and a cycle time of 0.5/sec to 1/sec (see also Carmeliet, 1961). Upon increasing the [Ca]0 the membrane hyperpolarized and the oscillations ceased.…”

Section: Effect Of Mn On the Ca Induced Decrease In Internal Namentioning

confidence: 93%

Changes in the intracellular sodium activity of sheep heart Purkinje fibres produced by calcium and other divalent cations.

Deitmer¹,

Ellis²

1978

The Journal of Physiology

121

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SUMMARY1. The intracellular Na activity of sheep heart Purkinje fibres was recorded with Na+-sensitive glass micro-electrodes. The effects of various external divalent cations on the intracellular Na activity were investigated.2. Raising the external concentration of divalent cations (Ca, Mg, Mn, Sr or Ba) from 3 to 16 mm resulted in a decrease in the intracellular Na activity of 10-50 %.3. Raising the external concentration of Ca, Sr or Ba could produce a decrease in the intracellular Na activity even when the Na-K pump was inhibited (with strophanthidin, 10-5 M); but raising the external concentration of Mg or Mn could not.4. Mn inhibited the decrease in the intracellular Na activity produced by raising external Ca while the Na-K pump was inhibited.5. Raising external Ca or adding Mn reduced the rate of rise of the intracellular Na activity on inhibition of the Na-K pump.6. The removal of external K resulted in an increase in the intracellular Na activity. This increase could be stopped and even reversed by raising external Ca.7. Removal of divalent cations from the external solution produced an increase in the intracellular Na activity. However, replacing external Ca and Mg by another divalent cation, e.g. Mn, did not result in a rise in the intracellular Na activity, except when the Na-K pump was inhibited.8. The intracellular Na activity decreased by approximately 50 % for a tenfold increase in the external Ca concentration.9. The extent of the decrease in internal Na activity produced by raising external Ca was directly proportional to the internal Na activity before external Ca was raised.10. We conclude that external Ca influences the intracellular Na activity in two ways: (a) by changing the passive Na influx: the resultant change in the intracellular Na depends on the activity of the Na-K pump; and (b) by a process where internal Na ions are exchanged for external Ca ions.

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“…It was assumed that Cl-was in electrochemical equilibrium. According to Carmeliet (1960) this is not the case (at least in Purkinje fibres), and in depolarized cells Cl-currents may contribute significantly to membrane conductance. Until these possibilities can be directly investigated in the septum further speculation is not worthwhile.…”

Section: Discussionmentioning

confidence: 99%

Sodium efflux in rabbit myocardium: relationship to sodium—calcium exchange

Bridge

Cabeen

Langer

et al. 1981

The Journal of Physiology

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SUMMARY1. The washout of 22Na, 45Ca and 58CoEDTA-has been observed in arterially perfused rabbit interventricular septa both in the presence and absence ofintoxicating doses of the aglycone, 3 acetylstrophanthidin (ACS).2. The washout of 22Na from paced septa (21P0/min) was rapid with approximately 99 % of the exchange occurring in 30 min.3. Septa labelled with 22Na and washed out in the presence of 10-5 M-ACS were quiescent, exhibited marked contracture and a slowed 22Na exchange with 99 % of the initial 22Na leaving the tissue in approximately 200 min.4. Comparison of the washout of the extracellular marker 58CoEDTA-from paced and intoxicated septa revealed no differences, suggesting that regions of the extracellular space had not become inexchangeable as a result of the contracture that these septa exhibited.5. Simultaneous measurements of the distribution of 22Na and 58CoEDTA-in the presence of 10-5 M-ACS revealed an apparent cellular Na concentration of 54-8 + 10-4 (S.E.). This was considerably in excess of the maximum amount of Na contributing to the slowest component of Na efflux from intoxicated septa. Origins of this discrepancy are considered.6. The slowest component of 22Na efflux from intoxicated septa could be markedly stimulated by increasing the external Ca concentration from a nominal 1-5 to 16 mM.The magnitude of stimulation was 44-3 + 7-8 % (S.E.). Increases in the concentration of Mg from 1-0 to 16-0 mm were without effect on the 22Na efflux.7. Application of 10-5 M-ACS produced marked depolarization of the membrane to new stable levels that lay between -10 and -20 mV.8. Washout of ACS after several hours of intoxication resulted in a partial decline in contracture tension, an acceleration of Ca efflux, little change in 22Na efflux and a repolarization of the cell membrane.

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Chloride ions and the membrane potential of Purkinje fibres

Cited by 216 publications

References 11 publications

Observations with endocardial electrography on ventricular tachycardia by intracoronary saline in dogs.

Observations with endocardial electrography on ventricular tachycardia by intracoronary saline in dogs.

Changes in the intracellular sodium activity of sheep heart Purkinje fibres produced by calcium and other divalent cations.

Sodium efflux in rabbit myocardium: relationship to sodium—calcium exchange

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